Duct seal

ABSTRACT

A rubber ring-shaped seal is provided with a centrally disposed ring-shaped elastomeric tubular insert mounted therein. A helical coil spring is mounted in the insert so that part of the ring-shaped insert is between the helical coil spring and the work-contacting surfaces of the seal. The seal is mounted on formations formed on a tubular housing which serves as a connector. These formations define seal-receiving channels which position the seal rings in the housing.

This is a division of application Ser. No. 212,028, filed Dec. 2, 1980 which was a continuation-in-part of patent application Ser. No. 181,411, filed Aug. 26, 1980, both of which are now abandoned.

This invention relates to a seal, and more particularly to a ring-shaped seal with a centrally disposed garter spring mounted therein.

Rubber seals, particularly those used in aircraft connectors and ducts, tend to leak when cold due to variations between the thermal coefficients of the material composing the seal and the metal ducts. This leakage tends to increase after a period of use, particularly when the seal is used at elevated temperatures because the rubber forming the seal "sets" and becomes less resilient.

One way to prevent this leakage is to provide the seal with a garter spring under tension which embraces the seal. With this arrangement, when the seal is on a duct or connector, the spring exerts a compressive or radially inwardly directed force on the seal, causing the seal to make a sealing engagement with the duct or connector at low temperatures, and even after the rubber in the seal has "set."

Elastomeric seal which have a spring under tension inside are typically formed from a silicon impregnated rubber with one or more laminations of silicon impregnated fiberglass cloth molded to and covering surface at least the surface of the seal which makes a sealing engagement with a surface on a connector or duct. The cloth covering is used because it is resistant to abrasion so that the life of the seal is prolonged. This is shown in the patent to Kramer, U.S. Pat. No. 3,918,726, and Greenwald, U.S. Pat. No. 3,698,727.

Heretofore, however, the seals were made so the garter springs inside the seal abutted the inner surface of the fiberglass cloth, see the patent to Greenwald, U.S. Pat. No. 3,698,727. As a consequence, when the seals were used in aircraft, vibration caused the springs to rub against the inner surface of the fiberglass cloth, wearing it through in a comparatively short time. This destroyed the surface that makes a sealing engagement with the work so that the seal had to be replaced.

Since seals in aircraft are positioned at various locations along the ducts in the aircraft, they are often mounted in locations which are hard to get at, and which require the disassembly of many aircraft parts to reach when the seals have to be replaced. This increases down time for the aircraft which greatly increases the cost of aircraft operation.

It is apparent that if the useful life of the seals could be increased, a disproportionately large savings in the cost of aircraft operation would result.

One way to increase the useful life of such seals is to prevent the springs mounted inside the seal from rubbing against the inner surface of the fiberglass cloth. If the spring, although under tension, could be held away from the inner surface of the cloth, then there would be a thickness of rubber between the spring and the inner surface of the fiberglass cloth. This would greatly prolong the useful life of the seal because before the spring could rub against and through the fiberglass cloth it would first have to rub through this thickness of rubber.

Heretofore, as exemplified by the patent to Weber, U.S. Pat. No. 3,406,979, efforts were made to solve the problem of centering a spring inside a seal. The Weber approach had a number of disadvantages. First of all, it required expensive hydraulic equipment. Secondly, it was time consuming because it required two separate molding steps, and it required the seal half sections to be preformed. Thirdly, "flash" formed on the work-engaging surfaces of the Weber seal. "Flash" is that part of the elastomeric material which forms at the junction of the mold, and in this instance it appears as irregular clumps of rubber. This "flash" had to be removed in order to form the sealing surface in the Weber seal, but it was time consuming and costly to do this. In addition, the work-engaging surfaces of the Weber seal was not composed of silicon impregnated fiberglass cloth so it did not have a sufficiently long, useful life.

What is needed, therefore, and comprises an important object of this invention is to provide a connector with a seal where the seal is formed from an elastomeric material with fiberglass cloth covering at least the work-engaging surface of the seal and where the seal has a spring under tension mounted inside the seal which is held in radially spaced relationship away from the inner surface of the fiberglass cloth.

This and other objects of this invention will become more apparent when better understood in light of the accompanying drawings and specifications wherein:

FIG. 1 is a plan view of a seal constructed according to the principals of this invention.

FIG. 2 is a sectional view taken on line 2--2 of FIG. 1.

FIG. 3 is an enlarged view of the region surrounded by the circular arrow 3--3 in FIG. 1.

FIG. 4 is an elevational view of the ring-shaped tubular insert with the coil spring inserted therein.

FIG. 5 is a cross-sectional view of the tubular insert with the coil spring in the tubular bore.

FIG. 6 discloses a ring-shaped seal, J-shaped in cross-section, with an elastomeric insert constructed according to the principles of this invention.

FIG. 7 discloses an enlarged portion of a double-sealed connector such as those shown in FIGS. 8 and 9, wherein the inner ring-shaped seal is constructed like the seal shown in FIG. 6, and the outer seal is constructed like the seal shown in FIG. 2.

FIG. 8 discloses an aligned double-seal restrained connector utilizing the double-seal structure shown in FIG. 7.

FIG. 9 discloses an offset double-seal connector utilizing the double-seal structure shown in FIG. 7.

FIG. 10 discloses an offset single-seal restrained connector with the seal shown in FIG. 2.

FIG. 11 discloses a conduit arrangement employing a single-seal bulkhead connector in combination with a restrained connector and the seal shown in FIG. 2.

FIG. 12 is a perspective view of a connector clamp used in combination with the restrained connector of FIG. 11.

FIG. 13 discloses a double-seal bulkhead connector wherein the inner seal is shown in FIG. 6 and the outer seal is shown in FIG. 2.

Referring now to FIG. 1 of the drawings, a ring-shaped O-ring type seal indicated generally by the reference numeral 10 is formed from an elastomeric material such as silicone impregnated rubber. Referring to FIG. 2, the seal 10 has a surface 12 which is covered by two layers of laminations of silicon impregnated fiberglass cloth 14 and 16 to form a continuous work engaging surface which is shaped to make a sealing engagement with a surface on a connector or duct. A ring shaped insert 18 comprising an elastomeric tube having a bore 20 and formed from silicone impregnated rubber is inside the seal and a garter or helical ring shaped coil spring 22 is inside the bore.

As seen in FIGS. 2 and 6, the garter spring (22) is held away from the inner surface (40) of the fiberglass layer (16) by the thickness of the walls of a tubular insert (18). Tension in the spring (22) inside the seal causes the seal to contract on and make a sealing engagement with the surface of a metal duct or connector even at low temperatures, and even after the rubber in the seal has hardened. Of course, aircraft vibration will cause the spring (22) in the seal to gradually wear away the silicon impregnated rubber between it and the inner surface (40) of the fiberglass layer (16). However, this will take some time, and finally when the coil spring has worn away enough rubber so it reaches the inner surface (40) of the fiberglass cloth (14), the useful life remaining in the seal would still be where it is in present seals where the coil spring rubs against the inner surface of the fiberglass cloth from the beginning of its use.

To vary the life of the seal, it would only be necessary to provide the tubular inserts (18) with walls which have a different thickness. Alternatively, the composition of the insert and the cloth layers (12) and (14) could be varied to change the ability of a seal to withstand abrasion and rubbing in acordance with special requirements.

To this point, the principles of this invention have been applied to the ring-shaped O-ring type seals shown in FIG. 1. However, they can also be applied to other kinds of seals in the connectors shown in FIGS. 6 to 12.

Seal (70) shown in FIG. 6 is ring-shaped and is generally channel-shaped in ross-section with leg portion (72) and (74), and a connecting web portion (76). The seal is formed from multiple laminations of silicon impregnated fiberglass cloth and is designed to be used in a connector such as the connector shown in FIG. 11 of the Greenwald patent, U.S. Pat. No. 3,698,727.

In FIG. 7, the leg portion (72) of seal (70) bears against the inturned flange or wall (102) in connector (90). This type of seal depends on temperature and the internal pressure in the duct or connector to deform the laminations of fiberglass cloth and force them into a sealing engagement with surfaces on the connector or duct.

Insert (18) with the garter spring (22) in bore (20) is mounted against the inner surface (78) of the web or semi-toroidal part (76) of the seal, and is sized so it exerts a compressive force on it. This causes the outer work-contacting surface (80) of the web portion (76) of the seal (70) to make a sealing engagement with seal-engaging surfaces on a duct, independent of temperature over a wide temperature range, see FIGS. 6 and 7.

It is apparent that the life of this kind of seal is greatly prolonged in comparison to prior seals of this kind, because before spring (22) can reach and rub through the lamination (61) and (63) of the fiberglass cloth it first has to rub through the thickness of the elastomeric insert (18), which is between the spring (22) and the inner surface (78) of the web portion (76). This arrangement is like the structure shown in FIG. 2 wherein the spring has to rub through the thickness of the elastomeric material in the insert which is between the spring (22) and the inner surface (40) of the fiberglass cloth.

If the seals constructed according to the principles of this invention are to be used in a particularly hot environment, in aircraft, where a seal failure could have very severe consequences, the connector (90) shown in FIG. 8 is particularly useful. This connector is provided with three counter bores (92), (94) and (96). In addition, an inwardly opened channel-shaped divider or seal-retaining ring (98) is secured to the counter bore (92) at the end of the connector (90) by welding or any other suitable means.

The ring-shaped seal (10) shown in FIG. 2 is mounted inside the channel defined by the seal-retaining ring (98). As seen, the seal is sized so a portion of the seal protrudes beyond the channel (100) for engagement with a seal-engaging surface on a duct. The seal-retaining ring (98) includes an outer leg or flange (101), an inner leg or flange (102), and a connecting web portion (104) which is secured by welding or any other suitable means to the inner surface of the counter bore (22). The inner leg or flange (102) of the seal-retaining ring (98) serves as a divider separating the outer seal (10) from the inner seal (70) and provides an additional fire-resistant protective surface.

Insert (18) mounted on seal (70) as shown in FIG. 6 causes the seal to exert a radially inwardly directed force on the ducts (106) and (108) mounted in connector (90) as shown in FIG. 8. With this arrangement, as the web portion (76) of the seal (70) hardens with use, the inwardly directed force exerted by the insert (18) on seal (70) maintains a sealing engagement between the web portion (76) of a seal and the outer seal-engaging surfaces of the ducts (106) and (108).

As seen in FIGS. 7, 8 and 9, the base (110) of the counter bore portion (96) is in spaced relation to the inner surface of the leg (74) of seal (70). This is important because it permits nondestructive flexing of the leg (72) and (74) of the seal (70) when the end of the ducts (106) or (108) pivot inside the connector (90). Without this arrangement the inner seal would wear rapidly and failure could occur after a comparative short time. The double-seal connectors shown in FIGS. 8 and 9 provide an additional margin of safety because if the inner seal fails, the outer seal would prevent the hot gases from escaping.

As a further protection for the seals against very high duct temperatures and pressures, the ducts (106) and (108) include sleeves (112) and (114) which are secured by welding or any other suitable means to the ends of the ducts. The seal-engaging surfaces of these sleeves are in spaced relationship to the outer surface (116) and (118) of the ducts defining an insulating air space (120) and (122) between the surfaces (116) and (118) of a duct and the seals (18) and (70), see FIG. 8. This also greatly extends the life of the seals because the temperature of the seals is greatly lessened.

The ducts (106) and (108) are provided with ring-shaped radially outwardly extended collars (124) and (126) which embrace their outer surfaces (116) and (118) and are secured thereto by welding or any other suitable means. These collars are channel-shaped in cross-section as shown in FIG. 8. A number of cables (128), in accordance with the strength required, are connected beween the collars in uniformly angularly spaced relationship around the axis of the collars to hold the ducts inside the connector (90) against high gas pressures inside them. The tightness of these cables can be adjusted by any suitable means mounted on the collars.

Seals (10) and (70) used with connector (68) can also be applied to offset connectors (130) as shown in FIG. 9. The offset connectors are used to connect ducts or tubes in aircraft where the axes of these ducts are offset or misaligned from each other. As seen in FIG. 9, the opposite ends of connector (130) are not in alignment with each other, but they are designed to be aligned with and receive ducts (132) and (134) as shown. The end portions of the offset connector (130) are like that shown in FIG. 7. Cylindrical sleeves (136) and (138) are secured by any suitable means to the outer surfce of a duct, and the inner end of the sleeves are bent radially outwardly to define collars (140) and (142). Restraining cables (144) are mounted on these collars in uniformly angularly spaced relationship around the axes of the ducts to hold the ducts inside the connector (130). Any suitable means, not shown, can be provided to tighten these cables as required.

The offset connector (146) shown in FIG. 10 is like that shown in FIG. 9, except that it employs a single seal (10) at each end instead of the double-seal arrangement shown in FIG. 9.

Aircraft have many bulkheads through which the ducts must pass. These often require the use of a bulkhead connector. As shown in FIG. 11, the single seal bulkhead connector (148) is provided with a radially outwardly extending mounting flange (150) mounted at one end and secured by any suitable means to the outer surface of the inner end of the bulkhead (152), see FIG. 11. The bulkhead (152) is provided with a bore (154) sized to permit a duct (156) to pass through. Similarly, the inner end of the bulkhead connector (148) is sized to permit the entry of the duct. The bulkhead connector is provided with a radially inwardly open seal-receiving channel (158) at its inner end. Seal (10) is mounted therein and is sized so it is in sealing engagement with the outer surface of the duct (156). The opposite end (160) of the bulkhead connector (148) extends inside one end of a connector (162). This connector is provided with rib-like radially outwardly extending inwardly open seal-receiving channels (163) and (165) at each end in which the seals are mounted. Another duct (164) is mounted on the opposite end of connector (162). In order to hold the duct (164) and the end of the other end of the bulkhead connector (148) inside the connector (162) against high gas pressure, a generally cylindrical split clamp ring (166) is mounted on the outer surfaces of the bulkhead connector (148) and the duct (164) and tightened thereon by bolt (168) and nut (170) shown in FIG. 12. The clamp ring (166) is provided with three integrally attached claws (172) disposed in uniformly angularly spaced relationship around the periphery of the clamp ring. These claws fit over the radially outwardly extending heat-radiating surface of the seal cooling and retaining channels (163) and (165) as shown in FIG. 11. In this way, when the clamp rings are tightened on duct (164) and the bulkhead connector (148) with the claws (172) extending over the outer surface of the rib-like seal ring receiving channels (163) and (165), the bulkhead connector (148) and the duct (164) are held securely inside the connector (162).

In some circumstances, where special conditions of high temperature and aircraft vibrations require it, the bulkhead connector (170) shown in FIG. 13 may be used. This connector is provided with inner and outer seals (70) and (10) mounted in the seal ring receiving channels (172) and (174). This portion of a double-seal bulkhead connector would be shaped like the portion of the connector shown in FIG. 7. 

Having shown and described the invention, what I claim is new is:
 1. An aircraft duct connector to be used with aircraft ducts, comprising a tubular housing, counter bores formed on at least one end of said tubular housing for positioning seal rings in said housing in spaced side-by-side relationship, outer and inner seal rings mounted in the counter bores at at least one end of said tubular housing, means in said housing cooperating with said counter bores to hold said seal rings in said spaced side-by-side relationship, said outer seal ring being solid and generally circular in cross-section and having an inner surface, said inner surface formed from an elastomer impregnated fabric and comprising a work-engaging surface adapted to make a sealing engagement with a surface on a duct, said outer seal ring further including a generally tubular ring-shaped insert engaging the surfce of said fabric opposite said work-engaging surface, said insert being formed from an elastomeric material, a ring-shaped spring mounted inside said tubular ring-shaped insert with the spring surrounded by and engaging the inner walls of the tubular insert and in such a way that at least part of said ring-shaped insert is between said spring and said fabric to hold said spring away from said fabric, said spring sized so when said seal is mounted on a duct said spring maintains the said work-engaging surface of the seal in sealing engagement with a surface on a duct independent of temperature over a wide temperature range, said inner seal ring including a lamination of elastomer impregnated fabric and being generally channel shaped in cross-section with radially outwardly extending legs and a connecting web, the web of said lamination having a work contacting surface and an opposite surface, the radial outer end of one of said legs being spaced from said tubular housing both to prolong seal life and to communicate duct pressure to the interior of the tubular housing between said legs, the work contacting surface of the inner seal ring adapted to be in sealing engagement with a surface of a duct whereby the inner seal ring can withstand high duct pressures while maintaining sealing contact, said inner seal ring including a tubular ring-shaped insert formed from an elastomeric material mounted on the surface of the lamination of said inner seal ring opposite said work contacting surface, a ring-shaped spring mounted inside the tubular insert of the seal ring with said spring engaging the inner walls of the tubular insert so that a thickness of the elastomeric material composing the insert is between the spring and the said opposite surface of the web, said spring sized so as to exert a compressive radially inwardly directed force on the web of said inner seal ring to maintain the work contacting surface of the inner seal ring in sealing engagement with a surface on a duct independent of temperature over a wide temperature range.
 2. The seal ring described in claim 1 wherein said inner surface of said outer seal ring is formed from at least one lamination of an elastomer impregnated fabric. 